A mileage of about 108,000 km BYD F3 sedan. Reflects the owner: high car engine coolant temperature.
Troubleshooting: After receiving the car, first verify that the failure phenomenon. Check the cooling fan is not found in the car, after turning on the air conditioner bmw diagnostic tool switch, condenser fan rotation, initially identified the car engine coolant temperature is high due to the cooling fan failure is a result of not working. Find car cooling fan and condenser fan control circuit (Figure 1), under normal circumstances, when the ignition switch is in the ON block, the 1st ignition relay, then press the air conditioner switch, the engine ECM controls the fan on the 1st relay and fan the 3rd relay, condenser fan relay started working, the cooling fan speed rotation, at this time, adjust the resistance in series with the electronic fan cooling fan circuit; when the engine coolant temperature reaches 98 ℃ ~ 100 ℃ or air conditioning pressure switch terminal 2 and terminal 4 turns (medium voltage protection), the engine ECM controls the fan on the 2nd relay, high-speed rotation of the cooling fan, this time, the electronic fan adjust the resistance no longer string into the cooling fan circuit. As the car condenser fan is working properly, but the cooling fan is not working, so you can troubleshoot engine ECM control of the main causes of failure hud may have a cooling fan and wiring harness is bad in itself fails, the cooling fan itself is damaged, the fan on the 1st relay or fan the 2nd relay internal faults.
According to the principle of simple to complex troubleshooting, first check the cooling fan wire connector situation and found no abnormalities; separate cooling fan powered cooling fan is rotated normally, so you can rule out the possibility of failure of the cooling fan itself; replace the fan a No relay, the cooling fan is still not working; in the repair process, try to unplug the coolant temperature sensor wire connectors, find the cooling fan speed rotation (if the coolant temperature sensor circuit, the engine ECM will think the engine is a large load of work, thereby controlling the speed of rotation of the cooling fan, which is determined from the fan on the 2nd relay after grounding resistor fan speed control circuit low-speed operation problems. unplug the fan on the 2nd relay checked and found the car was a four terminals installed relay view schematics, fan installed on the 2nd relay car relay terminals should be five. ask the owner kess v2 ecu programmer that the car had previously been in the repair shop for maintenance of other aspects of air conditioning failure, analysts believe may be time to replace the maintenance technician when the relay, did not pay attention, put a 4 terminal relay, the car fitted with four terminals after the relay, electronic fan adjust the resistance will be presented off state, resulting in failure of the cooling fan low speed does not work.
Troubleshooting: put 5 Terminal fan relay after the 2nd test, a cooling fan is working properly, the engine coolant temperature is not there fault, the fault completely ruled out.
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